Devices for sourcing 2D video data are known, for example video players like DVD players or set top boxes which provide digital video signals. The source device is to be coupled to a display device like a TV set or monitor. Image data is transferred from the source device via a suitable interface, preferably a high-speed digital interface like HDMI. Currently 3D enhanced devices for sourcing three dimensional (3D) image data are being proposed. Similarly devices for display 3D image data are being proposed. For transferring the 3D video signals from the source device to the display device new high data rate digital interface standards are being developed, e.g. based on and compatible with the existing HDMI standard. Transferring 2D digital image signals to the display device usually involves sending the video pixel data frame by frame, which frames are to be displayed sequentially. Such frames may either represent video frames of a progressive video signal (full frames) or may represent video frames of an interlaced video signal (based on the well known line interlacing, one frame providing the odd lines and the next frame providing the even lines to be displayed sequentially).
The document U.S. Pat. No. 4,979,033 describes an example of traditional video signal having an interlaced format. The traditional signal includes horizontal and vertical synchronization signals for displaying the lines and frames of the odd and even frames on a traditional television. A stereoscopic video system and method are proposed that allow synchronization of stereoscopic video with a display that uses shutter glasses. The odd and even frames are used to transfer respective left and right images of a stereoscopic video signal. The proposed 3D display device comprises a traditional envelope detector to detect the traditional odd/even frames but instead generates display signals for left and right LCD display units. In particular equalization pulses occurring during the vertical blanking interval, which differ for odd and even frames in the traditional interlaced analog video signal, are counted to identify the respective left or right field. The system uses this information to synchronize a pair of shutter glasses, such that the shutter glasses alternately open and close in sync with the stereo video.